Engine with exhaust cooling and method

ABSTRACT

An engine arrangement includes an engine, an exhaust line downstream of the engine, an aftertreatment device in the exhaust line, and a conduit between a source of fluid and a point in the exhaust line upstream of the aftertreatment device. A method is also disclosed.

BACKGROUND AND SUMMARY

The present invention relates to engine exhaust systems and, moreparticularly, to engine exhaust systems having exhaust cooling.

In many modern vehicles, such those including diesel engines, exhaustaftertreatment devices such as diesel particulate filters (DPF),selective catalytic reduction catalysts (SCR), and NOx traps areprovided in the exhaust line downstream of the engine. Devices such asthe SCR and NOx traps are typically disposed downstream of the DPF. Itis periodically necessary to regenerate the DPF, which usually involvesburning fuel upstream of the DPF to raise the temperature of the gaspassing through the DPF to temperatures that are potentially harmful toother devices. To avoid damage to the downstream devices, it iscustomary today to control the temperature of the gas passing throughthe DPF, such as by reducing the amount of fuel burned to regenerate theDPF. Nonetheless, it is still possible to generate excess heat which candamage the downstream devices.

It is desirable to provide an apparatus and method that can reduce thepotential for damage to aftertreatment devices downstream of a DPF.

According to an aspect of the present invention, an engine arrangementcomprises an engine, an exhaust line downstream of the engine, anaftertreatment device in the exhaust line, and a conduit between asource of fluid and a point in the exhaust line upstream of theaftertreatment device.

According to another aspect of the present invention, a method ofcontrolling temperature in an exhaust line is provided. According to themethod, exhaust temperature in an exhaust line is measured at a pointupstream of an aftertreatment device. A signal is sent to a controllercorresponding to the measured temperature. Air is introduced to theexhaust line at or upstream from the measuring point under control ofthe controller as a function of the measured temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in connection with a preferred embodimentshown in the following drawings in which:

FIG. 1 is a block diagram showing an engine with exhaust coolingaccording to an embodiment of the present invention; and

FIG. 2 is a block diagram showing an engine with exhaust coolingaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows an engine arrangement 21 according to an embodiment of thepresent invention. The engine arrangement 21 comprises an engine 23 andan exhaust line 25 downstream of the engine. An aftertreatment device 27is provided in the exhaust line 25. A conduit 29 extends between asource of fluid and a point 31 in the exhaust line 25 upstream of theaftertreatment device 27.

The source of fluid is ordinarily an intake line 33 upstream of theengine 23, however, it will be appreciated that fluid can be introducedfrom a variety of sources, such as pressurized air that is notcombustion air. Also, as seen in FIG. 2, an aspect of the enginearrangement 121 may involve introduction of fluid from a source of fluidsuch as a source of water 131 through a conduit 129. The enginearrangement 121 can be used instead of or in combination with the enginearrangement 21 shown in FIG. 1. FIG. 1 shows, in phantom, a source offluid that comprises a line 33 x that may be draw atmospheric air, forexample, together with a compressor 33 y for pressurizing the air to apressure sufficient to permit it to be introduced to the exhaust line25. This source of fluid may be a vehicle's compressed air system, suchas the system that is used for braking in trucks. For purposes ofdiscussion, an embodiment wherein the source of fluid comprises theintake line 33 will be described.

A temperature sensor 35 can be provided proximate the point 31 in theexhaust line 25. A controller 37 can be provided for receiving a signalfrom the temperature sensor 35. A valve 39 can be provided in theconduit 29. The valve 39 will ordinarily be controlled by the controller37 in response to the signal from the temperature sensor 35. The valve39 can be a proportional valve of the type adapted to be controlled bythe controller 37 to open to any of a plurality of positions betweenfully open and fully closed in response to the signal from thetemperature controller. The valve 39 may, of course, be of the on/offtype, e.g., a solenoid valve, that is either fully open or fully closed.Introduced air can be introduced continuously or in a series of pulsesuntil a desired temperature is reached.

A second temperature sensor 41 can be provided proximate a point 43where the conduit 29 connects to intake line 33. The controller 37 canreceive a temperature signal from the second temperature sensor 41, andthe controller can control the valve 39 as a function of the signal fromthe first temperature sensor 33 and the signal from the secondtemperature sensor 41. A charge air cooler (CAC) 45 is often provided inthe intake line 33. The conduit 29 is typically connected to the intakeline 33 downstream of the CAC 45 to take advantage of the cooler airdownstream of the CAC. It will be appreciated, however, that airupstream of the CAC can be used to cool the exhaust.

An upstream aftertreatment device 47 can be provided upstream of theaftertreatment device 27. The point 31 in the exhaust line 25 can bedisposed between the upstream aftertreatment device 47 and theaftertreatment device 27. In an embodiment that is presentlycontemplated, the upstream aftertreatment device 47 is a DPF, and thedownstream aftertreatment device 27 is at least one of a DPF, a NOxtrap, and an SCR. As regeneration of the DPF typically requirestemperatures that are higher than normal operating temperatures, coolingof the exhaust downstream of the DPF by introducing air to the exhaustcan reduce the possibility of damage to equipment such as an SCR or aNOx trap. When air is introduced from the intake line 33, it ispresently contemplated that approximately 10-15% of charge air will bediverted to the conduit 29 for introduction to the exhaust line 25.

In a method of controlling temperature in an exhaust line 25 accordingto an aspect of the present invention, exhaust temperature is measuredin the exhaust line at a point 31 upstream of an aftertreatment device27. A signal is sent to a controller 37 corresponding to the measuredtemperature. Air is introduced to the exhaust line 25 at or upstreamfrom the measuring point 31 under control of the controller 37 as afunction of the measured temperature.

The method can also comprise measuring a temperature of the airintroduced to the exhaust line 25, e.g., via the second temperaturesensor 41 proximate the point 43 in the intake line 33. A signal is sentto the controller 37 corresponding to the measured introduced airtemperature, and introduction of air to the exhaust line 25 iscontrolled by the controller 37 as a function of the measuredtemperature and the measured introduced air temperature.

A particularly beneficial use for an aspect of the present invention isin connection with cooling of exhaust from an upstream aftertreatmentdevice 47 such as a DPF that is upstream of an aftertreatment device 27such as an SCR or an NOx trap when the temperature of the exhaust at theupstream aftertreatment device is raised from a normal operatingtemperature. This may occur when, for example, a regeneration procedureis performed for the DPF which necessitates raising the upstreamtemperature from the normal operating temperature.

The method can comprise measuring a second exhaust temperature in theexhaust line 25 with a temperature sensor 49 at a second point upstreamof a second aftertreatment device 51. The temperature sensor 49 can senda signal to the controller 37 corresponding to the second measuredtemperature. Air can be introduced to the exhaust line 25 at a point 53at or upstream from the temperature sensor 49 under control of thecontroller 37 as a function of the second measured temperature. Theamount of air introduced can be controlled using a valve 55 that can beof ally desired type, but will ordinarily be of the same type used forthe valve 39.

In the present application, the use of terms such as “including” isopen-ended and is intended to have the same meaning as terms such as“comprising” and not preclude the presence of other structure, material,or acts. Similarly, though the use of terms such as “can” or “may” isintended to be open-ended and to reflect that structure, material, oracts are not necessary, the failure to use such terms is not intended toreflect that structure, material, or acts are essential. To the extentthat structure, material, or acts are presently considered to beessential, they are identified as such.

The invention must not be regarded as being limited to the exemplaryembodiments described above, a number of further variants andmodifications being feasible without departing from the scope of thefollowing claims.

1. An engine arrangement, comprising: an engine; an exhaust linedownstream of the engine; an aftertreatment device in the exhaust line;an upstream device upstream of the aftertreatment device; a conduitbetween a source of cooling fluid and a point in the exhaust lineupstream of the aftertreatment device and disposed between the upstreamdevice and the aftertreatment device; a temperature sensor proximate thepoint in the exhaust line; a controller for receiving a signal from thetemperature sensor; a valve in the conduit, the valve being controlledby the controller in response to the signal from the temperature sensorfor selective introduction of cooling fluid into the exhaust line; and asecond temperature sensor proximate a point where the conduit connectsto the source of fluid, the controller receiving a signal from thesecond temperature sensor, the controller controlling the valve as afunction of the signal from the first temperature sensor and the signalfrom the second temperature sensor, wherein the aftertreatment devicecomprises an SCR arranged to be operated within a predetermined range oftemperatures, the upstream device is adapted to at least occasionallyoperate at a temperature greater than an upper temperature of the rangeof temperatures, and the valve is controlled by the controller tointroduce cooling fluid into the exhaust when the upstream device isoperated at or above the upper temperature.
 2. The engine arrangement asset forth in claim 1, wherein the controller is adapted to control thevalve to open to a plurality of positions between fully open and fullyclosed in response to the signal from the temperature controller.
 3. Theengine arrangement as set forth in claim 2, comprising a secondtemperature sensor proximate a point where the conduit connects to thesource of fluid, the controller receiving a signal from the secondtemperature sensor, the controller controlling the valve as a functionof the signal from the first temperature sensor and the signal from thesecond temperature sensor.
 4. The engine arrangement as set forth inclaim 3, wherein the controller is adapted to control the valve to opento a plurality of positions between fully open and fully closed inresponse to the signal from the temperature controller.
 5. The enginearrangement as set forth in claim 1, wherein the controller is adaptedto control the valve to open to a plurality of positions between fullyopen and fully closed in response to the signal from the temperaturecontroller.
 6. The engine arrangement as set forth in claim 1, whereinthe source of fluid comprises an air intake line upstream of and leadingto the engine.
 7. The engine arrangement as set forth in claim 6,comprising a charge air cooler in the intake line, the conduit beingconnected to the intake line downstream of the charge air cooler.
 8. Theengine arrangement as set forth in claim 1, wherein the source of fluidcomprises a compressor.
 9. The engine arrangement as set forth in claim1, wherein the upstream device comprises an upstream aftertreatmentdevice upstream of the aftertreatment device, the point in the exhaustline being disposed between the upstream aftertreatment device and theaftertreatment device.
 10. The engine arrangement as set forth in claim9, wherein the upstream aftertreatment device is a DPF.
 11. The enginearrangement as set forth in claim 1, wherein the source of fluidcomprises a source of water.
 12. The engine arrangement as set forth inclaim 1, wherein the source of fluid comprises a compressor of aturbocharger of the engine.
 13. A method of controlling temperature inan exhaust line, comprising: measuring exhaust temperature in an exhaustline at a point upstream of an aftertreatment device, the aftertreatmentdevice comprising an SCR operable within a predetermined range oftemperatures; operating a device upstream of the aftertreatment deviceat a temperature above an upper temperature of the range oftemperatures; sending a signal to a controller corresponding to themeasured temperature; introducing a cooling fluid to the exhaust line ator upstream from the measuring point when the upstream device isoperated at the temperature at or above the upper temperature bycontrolling a valve with the controller as a function of the measuredtemperature, the valve being disposed in a line between the exhaust lineand a source of the cooling fluid; measuring a temperature of the fluidintroduced to the exhaust line, sending a signal to the controllercorresponding to the measured introduced fluid temperature, andcontrolling introduction of fluid to the exhaust line as a function ofthe measured temperature and the measured introduced fluid temperature.14. The method of controlling temperature in the exhaust line as setforth in claim 13, wherein the upstream device is an upstreamaftertreatment device, the method comprising introducing exhaust to theupstream aftertreatment device upstream of the aftertreatment device atan upstream temperature and raising the upstream temperature.
 15. Themethod of controlling temperature in the exhaust line as set forth inclaim 13, comprising measuring a second exhaust temperature in theexhaust line at a second point upstream of a second aftertreatmentdevice, sending a signal to the controller corresponding to the secondmeasured temperature, and introducing fluid to the exhaust line at orupstream from the second measuring point under control of the controlleras a function of the second measured temperature.
 16. The method ofcontrolling temperature in the exhaust line as set forth in claim 13,wherein the exhaust line is connected downstream of an engine and anintake line is connected upstream of the engine, comprising introducingbetween 10-15% of intake fluid to the exhaust line.
 17. The method ofcontrolling temperature in the exhaust line as set forth in claim 13,comprising introducing the cooling fluid by withdrawing the coolingfluid from a compressor of a turbocharger of an engine that exhaustsinto the exhaust line.
 18. An engine arrangement, comprising: an engine;an exhaust line downstream of the engine; an aftertreatment device inthe exhaust line; a DPF upstream of the aftertreatment device; a conduitbetween a source of cooling fluid and a point in the exhaust lineupstream of the aftertreatment device, the point in the exhaust linebeing disposed between the DPF and the aftertreatment device; a firsttemperature sensor proximate the point in the exhaust line; a secondtemperature sensor proximate a point where the conduit connects to thesource of fluid; a controller for receiving a signal from the firsttemperature sensor and a signal from the second temperature sensor andcontrolling the valve as a function of the signal from the firsttemperature sensor and the signal from the second temperature sensor;and a valve in the conduit, the valve being controlled by the controllerin response to the signal from the temperature sensor for selectiveintroduction of cooling fluid into the exhaust line, wherein theaftertreatment device comprises an SCR.
 19. The engine arrangement asset forth in claim 18, wherein the source of fluid comprises acompressor of a turbocharger of the engine.